The present invention relates to a fluorine-containing adhesive material which can firmly adhere to a substrate comprising an organic material such as a variety of synthetic resins or an inorganic material such as glass and metal. The present invention further relates to a laminate and a shaped article comprising the same as well as a process for producing the shaped article.
A fluorine-containing polymer has uses since it is excellent in heat-resistance, resistance to chemicals, weatherability, surface properties (a low frictional property and the like), and electrical insulation.
On the other hand, a fluorine-containing polymer is generally insufficient in mechanical strength and dimensional stability, and is expensive.
In order to utilize the advantages of a fluorine-containing polymer to a maximum degree and minimize the defects, this polymer has been extensively studied for its adherence or lamination with other organic materials and the inorganic materials.
However, a fluorine-containing polymer is inherently inert to the adhesion, and it is difficult to adhere a fluorine-containing polymer directly with the other materials (substrate). In many cases, even with heat fusing, the adhesion strength was insufficient and, even if adhered to some extent, the adhesion strength was widely varied depending upon the type of substrate, which reduces the reliance on the adhesionability.
As a method for adhering a fluorine-containing polymer to the other material, the following methods have been used:
(1) a method for physically roughing the surface of a substrate with sandblaster treatment,
(2) a method of treating the surface of a fluorine-containing polymer with sodium etching, plasma treatment, photochemical treatment or the like, and
(3) a method of adhesion using an adhesive have been mainly studied. However, regarding the above-mentioned (1) and (2), a treating step is necessary and, additionally, the productivity is low due to the complicated step. In addition, the type and shape of a substrate are restricted. Further, the adhesion strength is insufficient and a problem with appearance of the resulting laminate (coloration and flaw) easily arises.
The method and adhesive described in the above-mentioned (3) have drawbacks. Usual adhesives based on hydrocarbon materials have the insufficient adherability, and at the same time, they are insufficient in the heat resistance thereof. So then, they can not withstand the conditions for adhesion-processing a fluorine-containing polymer requiring molding and processing at an elevated temperature, in general, and peeling and coloration due to degradation occur. Since laminates using this adhesive are also insufficient in heat-resistance, resistance to chemicals and resistance to water of an adhesive layer, the adhesion strength can not be retained by a change in temperature and a change in circumstances, making this method less reliable.
The adhesion with an adhesive or an adhesive composition comprising s a fluorine-containing polymer having a functional group has also been studied.
For example, there are a report on the use of, as an adhesive, a fluorine-containing polymers obtained by graft-polymerization of a fluorine-containing polymer with a hydrocarbon monomer having a carboxyl group, a carboxylic anhydride residue, an epoxy group, or a hydrolyzable silyl group, representatives of which are maleic anhydride, vinyl trimethoxysilane and the like (for example, see JP-A-7-18035 (18035/1995), JP-A-7-25952 (25952/1995), JP-A-7-25954 (25954/1995), JP-A-7-173230 (173230/1995), JP-A-7-173446 (173446/1995) and JP-A-7-173447 (173447/1995)). There are also reports in which an adhesive composition comprising a fluorine-containing copolymer obtained by copolymerizing a hydrocarbon monomer containing a functional group, such as hydroxylalkyl vinyl ether and tetrafluoroethylene or chlorotrifluoroethylene, and an isocyanate as a curing agent, are used as an adhesive between vinyl chloride polymer and ETFE (ethylene/tetrafluoroethylene polymer) treated with corona discharge (for example, see JP-A-7-228848 (228848/1995)).
However, the adhesive and adhesive composition comprising a fluorine-containing polymer obtained by graft-polymerizing or copolymerizing a hydrocarbon functional monomer are insufficient in heat-resistance so that degradation and foaming occurs during a processing with a fluorine-containing resin at an elevated temperature or at the use of an elevated temperature, leading to decrease in the adhesion strength, peeling or coloration. In the case of using the above-mentioned adhesive composition described in the JP-A-7-228848 (228848/1995), the fluororesin requires corona discharge treatment.
In addition, it is reported that a fluorine-containing polymer having a functional group obtained by copolymerizing a perfluorovinylether compound containing carboxylic acid or its derivative with a fluorine-containing monomer is used as an adhesive or an adhesive composition. A laminate comprising a fluorine-containing polymer having a functional group introduced by copolymerizing perfluorovinylether having carboxylic group or its derivative with tetrafluoroethylene and the like is described in U.S. Pat. No. 4,916,020.
This is a laminate in which the aforementioned fluorine-containing polymer having carboxylic group or the like is laminated on a metal or the other substrate via an adhesive resin such as an epoxy resin and urethane resin and not a laminate in which the polymer is directly adhered to a metal, glass or other resins. Thus, there is a problem on heat-resistance, resistance to chemicals and resistance to solvent of an epoxy resin or an urethane resin upon use. In addition, although adhesion is possible via an epoxy resin or an urethane resin, a method for adhering directly to a metal, glass or other resins is not explicitly described.
An object of the present invention is to solve the aforementioned problems of the previous methods and materials and provide a fluorine-containing adhesive material which can directly impart the firm adhesion strength to a substrate, such as metal, glass and a resin, while maintaining excellent properties such as resistance to chemicals, resistance to solvent, weatherability, resistance to stain and unstackiness, which are general characteristics of a fluorine-containing polymer. The present invention also provides a laminate and a shaped article comprising the same. Another object of the present invention is to provide a fluorine-containing adhesive material which can firmly adhere to the above-mentioned substrate by, particularly, heat melting adhesion step, as well as a laminate comprising the same.
The fluorine-containing adhesive material of the present invention comprises a fluorine-containing ethylenic polymer having the number greater than the particular number of carbonate groups and/or carboxylic halide groups at an chain end or a side chain of a polymer. The present inventors discovered that the fluorine-containing adhesive material shows a surprisingly strong adhesion strength relative to a synthetic resin, a metal, a glass, and other materials without surface treatment or coating with an adhesive resin (such as a primer) normally performed in the case of the use of a fluororesin, when the number of carbonate groups and/or carboxylic halide groups of the fluorine-containing ethylenic polymer is greater than the particular number. The present inventors further discovered that a laminate retaining the better adhesion state and a shaped article comprising the same can be obtained by selecting the particular fluorine-containing ethylenic polymer and a counterpart material, and the particular shaping conditions.
The fluorine-containing adhesive material of the present invention has a carbonate group and/or a carboxylic halide group at an end or a side chain of polymer. When the material has the carbonate group, the material comprises a fluorine-containing ethylenic polymer having at least 150 carbonate groups relative to 1xc3x97106 main chain carbons. When the material has the carboxylic halide group, the material comprises a fluorine-containing ethylenic polymer having at least 150 carboxylic halide groups relative to 1xc3x97106 main chain carbons. When the material has both the carbonate group and the carboxylic halide group, the material comprises a fluorine-containing ethylenic polymer having totally at least 150 those groups relative to 1xc3x97106 main chain carbons. In the following explanation, a carbonate group and/or a carboxylic halide group are simply referred to as xe2x80x9ccarbonyl group-containing functional groupxe2x80x9d collectively.
The fluorine-containing adhesive material of the present invention comprises a fluorine-containing ethylenic polymer having a carbonyl group-containing functional group at a chain end or a side chain of the polymer and the number of the carbonyl group-containing functional groups is at least 150 relative to 1xc3x97106 main chain carbons. When the number is less than 150, the sufficient adhesion strength is not manifested or, even when adhered tightly, peeling easily occurs by deformation, a temperature change, or other environmental change. The number of carbonyl group-containing functional groups in the fluorine-containing ethylenic polymer of the present invention can be appropriately selected from a range of at least 150 depending on a type and shape of a substrate to be adhered, a purpose of adhesion, an application, a required adhesion strength, a form of an adhesive polymer and an adhering method. Preferably, the number of carbonyl group-containing functional groups is at least 250, more preferably at least 300 relative to 1xc3x97106 carbons. The upper limit number of carbonyl group-containing functional groups may be 3,000, preferably 2,000, for example 1,000. Too great of a number of carbonyl group-containing functional groups causes deterioration of heat-resistance and chemicals. The carbonate group is selected more preferably from a viewpoint of adhesion strength stability.
The fluorine-containing adhesive material shows the better initial adhesion strength, and the better durability against temperature change (for example, the use at a low temperature or a high temperature) and permeation of water and chemicals.